Nitro Boat Engine Problems

[Mavrick]

I just bought a used nitro boat with a 3.5cc K and B outboard. I'm having problems running it. It only has one fuel air adjustment and another screw which i think is the idle screw but i'm not sure, I'm new to this... It seems to be running extremely rich even if the air mixture needle is completely unscrewed from the carb. It seems like it floods really easily and if i can get it to start the throttle response is a joke. If i give it throttle it usually just chokes itself out. if it starts it will only run for about 5 seconds and then choke out and fuel will spit from the carb. The glow plug seems too be alright as long as i have a good battery in the igniter but I'm going to replace the plug to see if it makes a difference although i don really think its the main problem. Any adjustment i make on the fuel air needle it seems to me that its not really even doing anything. It just remains extremely rich. I actually took the needle right out of the carb and it ran better and i had some good throttle response but the rpms seems really high even though my idle trim on my remote was low. I'm having to do this out of the water because i don't have enough time to get it to the water without it dying on me. Also it dies immediately after i remove the glow igniter. Can someone please tell me whats going on here? Thanks

 

[mayrider]

If it is to rich you need to run needle in not out

 

[Nitro4910]

I assume it's one of these 3?
http://www.mecoa.com/kb/marine/marine_outboard.htm

First off read what the owners manual says about tuning & engine setup.
If it's running overly rich, lean it out some by turning the needle in.

 

[burnskevin58]

I just bought a used nitro boat with a 3.5cc K and B outboard. I'm having problems running it. It only has one fuel air adjustment and another screw which i think is the idle screw but i'm not sure, I'm new to this... It seems to be running extremely rich even if the air mixture needle is completely unscrewed from the carb. It seems like it floods really easily and if i can get it to start the throttle response is a joke. If i give it throttle it usually just chokes itself out. if it starts it will only run for about 5 seconds and then choke out and fuel will spit from the carb. The glow plug seems too be alright as long as i have a good battery in the igniter but I'm going to replace the plug to see if it makes a difference although i don really think its the main problem. Any adjustment i make on the fuel air needle it seems to me that its not really even doing anything. It just remains extremely rich. I actually took the needle right out of the carb and it ran better and i had some good throttle response but the rpms seems really high even though my idle trim on my remote was low. I'm having to do this out of the water because i don't have enough time to get it to the water without it dying on me. Also it dies immediately after i remove the glow igniter. Can someone please tell me whats going on here? Thanks

I know this an old post but the K&B outboard is still being used by people.
yes only one needle and a tiny hole to help with low to high speed.
The black carb what people don't understand is the idle position vs opening. one mm is all that's needed (The hole in the barrel is not 100% round and has a slight egg dome at the 12 o clock position of the hole in the barrel, that tiny shape is all that's needed for idle. if the opening is more than one mm the needle is also open more flowing more fuel into the carb/engine. (The needle moves with the barrel rotation).
20% fuel 3 1/2 turns on the needle is fine to get it running.
40% fuel 4 1/2 to 5 turns.

The 3.5cc outboard never had a crisp throttle response, more or less we would bleep them with the revs up and down and when ready to drop into the water (launch) the boat we would be at high rpm, once the engine warms up it will lean out and run better but they did and do run very bad on the shore.
K&B is also the only manufacture to tell you in the manual to not break the motor in on the bench, to simply start it and run it in the water to break it in. takes about one tank of fuel to break in a K&B inboard and outboard. But yes no low speed needle, just a tiny hole to spit fuel out of when the rpm lowers.

 

[alfredwong2003]

You can also buy a regular remote control carburetor. But you have to know what kind of fuel you are running with, I believe most people would be using 40% nitro. You kind of have to run it lean with a single needle carburetor.